Topic: black oil

[donny]

  how many miles do you get before the oil gets black?  i keep the oil changed in my truck changed enuf so it never gets dark, but I am somewhat new to mc.  My oil in the 750 seems to get dark way too early, and I am wondering if it is a sign of bad rings, or something?  BTW, I don't have a good exhaust system on it yet, 4 into 1,; 2' straight pipe with a holey red bull can shoved up it for some backpressure. It runs well, till I find a muffler of some kind that will fit.
     donny

[nickjtc]

What kinda oil are you using? Dark oil isnt necessarily a bad thing.  As long as youre changing the oil and filter when they need to be(around 1500 on these bikes) and you have a good air filter system on it you should be fine.  Rember this is detergent oil we are talking about and it is meant to clean as it lubricates and keep the dirt suspended which is why it gets dark.  So if the oil is within its sevice limit and is dark..well that just means its doing its job from what I understand.

I concur. Air cooled engines will 'cook' the oil quicker than liquid cooled due to the greater potential range of operating temperatures. Therefore it will turn black quicker. As long as you change your oil as indicated, and don't let it reach the point where the inside of the engine looks like it is coated with treacle (molasses to our North American friends) you're in great shape.

Do a compression/leak down test if you have concerns about the efficacy of the rings.

[supersport_CB400F]

Oil's a tuff one  but your truck thing sounds good, my 400 oil turs black after a couple hundred miles from what I remember but that was with mineral oil, I've had the engine open an no damage had been done.

[aptech77]

That means it is working

[Bob Wessner]

I've noticed the same thing on my 750 and attribute some of it at least to the start-up on choke, or half-choke running during warm-ups. Though brief, that's a pretty rich mixture.

Oh, and I have absolutely no scientific evidence whatsoever to support this. 

[mrbreeze]

If you have good power and your not seeing any smoke out of the tailpipe,I would'nt worry about rings.

[nickjtc]

I've noticed the same thing on my 750 and attribute some of it at least to the start-up on choke, or half-choke running during warm-ups. Though brief, that's a pretty rich mixture.

Oh, and I have absolutely no scientific evidence whatsoever to support this. 

.....but it sure sounds like a good theory, Bob!

[mrbreeze]

Choke on....runnin' rich(GAS SMOKE....BLACK!!!) Bad rings,valve guides,etc.....burning oil (BLUE SMOKE)..... White smoke....don't worry about it...its just condesation in the pipes(unless you have the extremely rare water cooled SOHC!!!!!!

[Heirborn]

I thought the oil was getting dirty way too early on my 750. After being better educated on the bike learned that the spring that keep pressure against the oil filter, to keep against the block, when in the housing was missing. I replaced it and the oil looks a lot better now.